The development of digital technology provided the ability to store and process vast amounts of information. While this development greatly increased information processing capabilities, it was soon recognized that in order to make effective use of information resources it was necessary to interconnect and allow communication between information resources. Efficient access to information resources requires the continued development of information transmission systems to facilitate the sharing of information between resources. One effort to achieve higher transmission capacities has focused on the development of optical transmission systems. Optical transmission systems can provide high capacity, low cost, low error rate transmission of information over long distances.
The transmission of information over optical systems is typically performed by imparting the information in some manner onto an optical signal. In most optical transmission systems the information is imparted by using an electrical data stream either to directly modulate an optical source or to externally modulate an optical carrier so that the information is carried at the frequency of the optical carrier, or to modulate the information onto one or more subcarriers or sidebands, with the later technique sometimes called sub-carrier modulation (“SCM”).
Many variations of optical systems or networks are possible, including all-optical networks, point-to-point networks, other types of networks, and combinations thereof. Optical cross connects (OXC) may be used to multiplex traffic entering the network, and may be used for the intermediate grooming of traffic as it travels through the network. With point-to-point transmission architectures, where traffic is dropped or regenerated at every node, grooming adds only a relatively small additional cost at the node, and hence intermediate grooming can be performed as needed to maintain high channel utilization. In longer haul transmission architectures such as all-optical networks, extended long haul systems, and ultra-long haul systems, however, channels can pass through a node without transponders or regenerators, and the cost of grooming includes both OXC interfaces and WDM transponders.
Traditional mesh restoration designs attempt to minimize the spare bandwidth required for 100% recovery of the traffic from any single cable cut. With short optical reach, the cost of such designs is close to optimal. Maximizing bandwidth efficiency results in the assignment of spare bandwidth to short, highly shared links. However, this practice does not use ULH technology effectively.
In addition, the amount of broadband services (e.g., IP, private lines, . . . ) being deployed within core networks is large and ever increasing. Most of these services require sub-wavelength connectivity (e.g., OC-3/STM-1, OC-12/STM-4, . . . ) between network end-points, leading to the need for efficient grooming architectures supporting low-cost, efficient transport. Several alternative grooming architectures exist. Each provides different levels of network efficiency and cost. The different architectures offer significantly different performances when traffic growth and scalability is considered optical systems 10 may utilize different grooming architectures.
Furthermore, in an environment where capital and operational expenses are constrained by strong competitive pressures, the control plane becomes a critical component of the next-generation transport network. By automating provisioning operations, it reduces operational expenses. By automating traffic engineering, the control plane allows for maximizing revenue over deployed network resources. In particular, we show that for a given deployment network capacity, a larger set of traffic demands can be accommodated when allowing for dynamic reconfigurability, rather than using a static configuration. The Control Plane also holds the promise of generating additional revenues through next-generation services such as Bandwidth-on-Demand (BoD) and Optical Virtual Private Networks (OVPN).
Accordingly, there is a need for more efficient grooming, protection, restoration, and migration in modern networks, as well as a need for networks that are more flexible and more easily reconfigured to meet changing demands.